عملکرد لرزه ای اسکله های توخالی
Abstract
1. Introduction
2. Experimental program
3. Experimental observation
4. Analysis on test results
5. Discussion on influencing factors
6. Quantification of seismic performance objectives
7. Conclusions
Acknowledgments
References
Abstract
To investigate the seismic performance of railway bridge piers with round-ended hollow section, five 1/6-scale specimens were tested under low-cyclic loading. The two variable parameters were the volumetric stirrup ratio and axial load level. The damage evolution, strain response, and plastic hinge behavior were meticulously explored. The load-drift relationship, displacement ductility, strength/stiffness degradation, dissipated energy, and viscous damping were analyzed in depth. The quantification of seismic performance objectives was implemented by displacement ductility based on damage assessment. The relationships among the ductility and strength/ stiffness degradation and equivalent damping ratio were regressed using the test data. The experiment and analysis results showed that all specimens suffered flexural failure, with flexural cracks covering nearly twothirds of the pier height. The plastic hinge region lengthened and moved upwards along the column due to the existence of solid segment, internal chamfer and variable section. The displacement ductility capacity enhanced noticeably with increasing stirrup ratio. The increasing axial compression ratio led to higher initial stiffness and seismic capacity to some extent, but excessive axial load would decrease ductility with premature concrete crushing. Furthermore, the seismic safety of the piers were ensured under a ductility factor limitation of 4.8 required by the current seismic code for railway engineering of China.
Introduction
With the robust expansion of high-speed rail (HSR) network in recent years, a large number of standard short-span bridges (including simply supported beam bridges and a few continuous beam bridges) have been constructed or are being built in the southwest region of China [1,2]. To accommodate the rugged topography of mountainous areas, the height of these piers is usually over 30 m [3]. For slender railway bridge columns, the round-ended hollow piers are usually selected as the substructure [4], which not only saves material, lowers self-weight and reduces seismic inertial forces compared with traditional solid piers, but also meets with the stiffness requirement for HSR bridges. However, the Southwest China is known for frequent intensive earthquakes (such as the Wenchuan Earthquake in 2008 and the Lushan Earthquake in 2013). The railway bridges with thin-walled slender columns are vulnerable to seismic damage, so their seismic performance need to be studied in depth. To date, numerous experiments have been finished on rectangular (e.g., [5–10]) and circular (e.g., [11,12]) hollow columns. Mander et al. [5] concentrated on the seismic performance of rectangular hollow columns via semi-static tests of four reduce-scaled models. A series of experiments on full or reduce-scaled rectangular hollow columns were conducted by Yeh and Mo [6–۸] since 2000. Furthermore, biaxial quasistatic tests were also performed on rectangular hollow pier specimens [9,10]. For circular hollow piers, Zahn [11] and Yeh [12] studied the flexural strength and ductility behavior respectively.